The Cover Feature depicts supercapacitors based on hierarchically porous carbon electrodes and ionic liquid electrolyte. The mass-balancing strategy is easy to handle, whereas the pre-charging strategy can achieve a higher energy density. Consequently, the resultant two supercapacitors are able to operate at the theoretical voltage of 4.0 V along with superior energy densities of 112.33 Wh kg−1 and 132.56 Wh kg−1. More information can be found in the Article by M. Ye et al. on page 624 in Issue 3, 2020 (DOI: 10.1002/celc.201901922).
Abstract Currently, epoxy resin (EP) is widely used in various fields, but its flammability greatly limits the wider application of EP. In recent years, additive flame retardants have been widely used to enhance the flame retardancy of EPs, but poor resistance to weather and aging is a prevalent issue encountered with additive flame retardants. To improve the weather fastness, researchers have successfully created and synthesized EP molecules that possess a combined effect of P, N, and B. The results demonstrate a significant enhancement in the mechanical properties of materials containing 20% BVN/10% VPD/EP compared with those of pure EP. 20% BVN/20% VPD/EP exhibited a vertical combustion rating of V‐1 with a limiting oxygen index measuring at 29.8%. The flame retardant epoxy thermosets exhibited a notable decrease in both the maximum heat release rate and total heat release. The findings indicate that the inherent flame‐retardant properties of the P‐N‐B coacting EP are not only characterized by exceptional curing and flame retardancy but also by superior resistance to weathering and aging compared with the additive flame retardant.
Abstract In this study, a cyclotriphosphazene hyperbranched P/N/Si prepared flame retardant (HBPPSi) was synthesized, and the effects of different loadings of HBPPSi on the mechanical properties, thermal stability and flame retardancy of epoxy resin were investigated. The mechanical property studies showed that the addition of HBPPSi could effectively improve the strength and toughness of epoxy resin, in which the strength and toughness of 5% HBPPSi/EP composites were improved by 43% and 59%, respectively. Meanwhile, thermogravimetric analysis and combustion performance test analysis indicated that the loading of HBPPSi could significantly improve the carbon formation rate, flame retardancy, and smoke suppression performance of EP composites. 5% HBPPSi/EP composites achieved a V‐1 grade in the UL‐94 test, and the LOI value increased to 28.3%. Compared with the pure EP material, the maximum heat release rate (PHRR) and total smoke release (TSP) of the 5% HBPPSi/EP composite were reduced by 47% and 32%, respectively. In addition, the release of toxic smoke CO was also significantly reduced. More importantly, the mode of action of the effect of HBPPSi on the mechanical properties, flame retardant properties, and smoke suppression properties of EP materials was investigated.
Because of easy functionalization, low cost, and large-scale fabrication, pure organic fluorescent polymers are widely applied in light-emitting display, bio-fluorescence-enhanced imaging, explosive detection, and other fields. Among these applications, due to their unique optical rotation characteristics, chiral fluorescent polymer materials are part of fluorescent polymers which could be used in chiral molecular detection and separation, biological target detection, etc. In this work, we designed and synthesized the first chiral organic fluorescent polysulfate materials through sulfur fluoride exchange polymerization (new click chemistry) by asymmetric binaphthol molecular. The chiral fluorescent polysulfate were synthesized by R/S [1,1′-binaphthalene]-2,2′-diol(Binol.), propane-2,2-diylbis(4,1-phenylene) bis(sulfurofluoridate) (FO2S–BA–SO2F) and 4,4′-(propane-2,2-diyl)diphenol(BA.) through step-by-step polymerization reaction under alkali present. It was found that the local crystallization of pure bisphenol A polysulfate was broken by the asymmetric axial chiral BINOL molecule inserted in it and let the polymer into the amorphous state. Fluorescent chiral molecules are uniformly dispersed in the polymer; the 120 µm film prepared by the film scraper was transparent and had good luminescence characteristics under ultraviolet light. After fluorescence detection, the excitation wavelength is 450 nm, and the emission wavelength is 480 and 517 nm.
Abstract The polystyrene (PS) composite containing self‐expanded intumescent flame retardant (polyphosphate ammonium and expandable graphite) was blended with three butyltriphenylphosphine‐based chelate borates, respectively, to evaluate their effect on flame retardancy. The chemical structure of as‐prepared three chelate borates was confirmed by nuclear magnetic resonance (NMR) and Fourier transform infrared spectrum (FTIR). The flame retardancy of various PS composites was evaluated by vertical burning test (UL‐94), limited oxygen index (LOI), and cone calorimeter (CC). Flammability and combustion results suggested that one of chelate borates, named [BTP][BMB], made PS composite (PS4) obtain V‐0 rating, 27.0 ± 0.3% LOI value, and reduction on heat release and smoke production with 17 wt% total flame retardants loading. The combustion residue was analyzed by scanning electron microscope and FTIR, and the pyrolysis gaseous products were investigated by TG‐FTIR technique. Besides, complex viscosity of PS composites composed of various chelate borates from a rheology instrument indicated that the improvements of flame retardancy of PS composites depended on the temperature of construction of crosslinked network by expandable graphite, which the chelate borates showed distinctive influence. Accordingly, the flame‐retarding mechanism about fast response to flame has been proposed.
Abstract In recent years, the poor weather resistance and aging resistance of additive flame retardants have caused researchers to pay attention to reactive flame retardants. A novel P‐N coacting epoxy curing agent with intrinsic flame retardancy was designed and synthesized. The mechanical properties, crosslinking curing properties and flame‐retardant properties of intrinsic flame‐retardant epoxy resin were characterized. The results show that the cross‐linking curing performance of hexa (3,5‐diamino‐1,2,4 triazolyl)‐cyclotriphosphonitrile) (VCP) is lower than that of DDM. This is due to the decrease in cross‐linking density caused by the VCP ring molecular structure. Therefore, the mechanical properties of the epoxy resin cured with VCP decreased, but the flame‐retardant properties of the material significantly improved. The limiting oxygen index of the VCP/EP flame retardant epoxy thermosets was 27.3%, reaching the UL 94 V‐1 level. The peak heat release rate and total heat release rate of the VCP/EP flame retardant epoxy thermosets were significantly reduced. The flame retardancy mechanism was studied by Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, and x‐ray photoelectron spectroscopy. The results show that the intrinsic flame‐retardant P‐N coacting epoxy resin has excellent curing and flame‐retardant properties.
Organic fluorescent materials are widely applied in different important fields, such as light-emitting display, explosive detection, molecular imprinting, and so on, because of their low cost, easy functionalization, and large-scale fabrication. In this work, we designed and synthesized a new kind of organic fluorescent polysulfate composite material through post-sulfonation sulfur-fluorine exchange polymerization (a new kind of click chemistry) by symmetric molecular. Sulfur-fluorine exchange polymerization: symmetrical structure SO2F−R1−SO2F molecular reacted with symmetrical OH−R2−OH molecular through nucleophilic reaction in the presence of inorganic base. The polysulfate material was further modified by ClSO3H to get PSE−SO3H materials. Tb3+ was highly dispersed on PSE−SO3H to afford organic-inorganic hybrid fluorescent materials through the conventional coordination chemistry method. The emission wavelength of the organic-inorganic hybrid fluorescent polymer PSE−SO3H−Tb3+ was between 475 and 685 nm, the quantum yield reached 1.18%, and fluorescence lifetime lasted for 730.168 us, with the pure green light emission and long light-emitting lifetime. The fluorescence film was prepared through phase transformation method by the fluorescent polymer material PSE−SO3H−Tb3+. The film has the strong stability property in different pH conditions (pH 1~13). Thus, this kind of organic fluorescent polysulfate composite material may have certain prospects application in terms of detection and luminescence in extreme chemical environments in the future.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)